*{ 
	margin: 0px;
	padding: 0px;
}
.heading{
	margin: 10px auto;
}
.heading{
	border:1px solid #ff0000;
	height:100px;
	background: #efefef;
}
.left,.main,.right{
	background: #00ff00;
}
.footer{
	height:100px;
	background: #ffff00;
}
@media screen and (min-width: 760px){
	.heading{
		font-size:30px;
		border:1px solid #efefef;
		height:100px;
		background: #ff0000;
	}
	.left,.right{
		font-size:30px;
		float: left;
		height: 500px;
		width:200px;
	}
	.main{
		font-size:30px;
		float: left;
		margin-left: 5px;
		margin-right: 5px;
		width:340px;
		height: 500px;
	}
	.footer{
		font-size:30px;
		clear: both;
	}
}
@media screen and (max-width: 400px){
	.left,.right{
		display: none;
	}
}
@media screen and (min-width: 400px) and (max-width: 760px){
	.left,.main{
		float: left;
		height:400px;
	}
	.right{
		display: none;
	}
	.left{
		width:30%;
	}
	.main{
		margin-left: 10px;
		width:65%;
	}
	.footer{
		clear: both;
	}
}